This invention relates generally to devices for making electrical connections between two sets of conductors. More particularly, this invention relates to connecting devices for use in the communications industry comprising two basic components, namely a wiring block and a connecting block wherein the connecting block includes a novel solderable or press-fittable tail for electrical and physical attachment to circuit board circuitry. Such tails extend from an electrical contact whose opposing end is suitable for the termination of insulated wires.
Wire connecting systems of the type described herein are well known and commercially available from AT&T Technologies as the 110 connector system. 110 type wiring systems are described in several prior patents including U.S. Pat. Nos. 3,611,624; 3,978,587 and 4,118,095.
Wire connecting blocks of the type disclosed in B. C. Ellis, Jr. U.S. Pat. No. 3,611,264 issued Oct. 5, 1971, include an indexing strip (wiring block) and a connecting block, the latter of which carries a plurality of slotted beam contacts. The indexing strip has a plurality of uniform height, spaced-apart teeth along its length. These teeth aid in indexing a first set of conductors. A corresponding plurality of uniform height, spaced-teeth carried by the connecting block serve to index a second set of conductors to be cross-connected through the slotted beam contact to the first set of conductors.
A number of improvements to the basic Ellis, Jr. connecting block are disclosed in B. C. Ellis, Jr. et al U.S. Pat. No. 3,798,587 issued Mar. 19, 1974. In the improved version, the spaced-apart teeth in both the indexing strip and the connecting block are staggered in height to facilitate indexing each set of conductors. The Ellis, Jr. et al connecting block is a two-piece structure comprised of matching halves which are secured together following insertion of the slotted beam contacts. However, it has been found that when the connecting block is placed over the indexing strip in cold temperatures, certain stresses are applied to the bond between the two connector parts. These stresses often rupture the bond causing failure of the entire unit.
The problems associated with U.S. Pat. No. 3,798,587 were improved upon in U.S. Pat. No. 4,118,095 issued Oct. 3, 1978 to Berglund et al. As in U.S. Pat. Nos. 3,611,264 and 3,798,587, Berglund et al relates to a wire connecting block which includes a pair of mating connectors (e.g., connecting block and wiring block) for effecting electrical cross-connections between a first set of conductors and a second set of conductors. The first connector indexes the first conductors and holds them in alignment for engagement with a plurality of insulation-penetrating slotted beam contacts carried by the second connector.
Rather than the connecting block comprising two substantially matching halves as in U.S. Pat. No. 3,798,587, in the Berglund et al patent, the connecting block comprises a housing which mates with a discrete anchoring member. The separate anchoring member is a molded piece which acts to position and retain the plurality of spaced beam contacts.
While the use of the housing/anchoring member presents an improvement to the structure of U.S. Pat. No. 3,798,587, the Berglund et al structure nevertheless suffers from certain deficiencies and drawbacks. For example, the connecting block of Berglund et al is still comprised of two discrete molded parts (e.g., the housing member and the anchoring member). The use of the second molded part (e.g., anchoring member) to hold in contacts increases assembly time, inventory, tooling cost and, consequently, the overall cost of the part to the end user. In addition, the second molded part (e.g., anchoring member) may be removed (for example, due to a faulty ultrasonic weld) thereby destroying the connector assembly.
Another detrimental characteristic of prior art connecting blocks described in U.S. Pat. Nos. 3,611,264; 3,798,387 and 4,118,095 results from the requirement that they be continuously end stackable on the wiring block. Because the existing embodiments or prior art designs preserve the contact center spacing to maintain precise alignment with the mating receptacles on the wiring block, the resulting insulating barrier that confines the outside surfaces of the end contacts is thin, and therefore prone to breakage when required to terminate the large wire gauges (e.g., 22 AWG wire) presently in use for data transmission applications. When such breakage occurs on the ends of adjacent connecting block modules, electrical shorting results.
U.S. Pat. No. 4,964,812, which is assigned to the assignee hereof and incorporated herein by reference, provides significant improvements to the above-discussed connecting blocks. In accordance with U.S. Pat. No. 4,964,812, a wire connecting system is provided which includes a pair of mating connectors for effecting electrical cross connections between a first set of conductors and a second set of conductors. The two mating connectors are known by the terms "wiring block" and "connecting block" wherein the wiring block provides evenly spaced receptacles for the first wire conductors that hold them in alignment for engagement with a plurality of insulation penetrating slotted beam contacts carried by the connecting block.
In accordance with an important feature of U.S. Pat. No. 4,964,812, the connecting block employs a novel one piece structure which both forms the connector block housing as well as provides retention means for positioning and retaining the slotted beam contacts. These retention means comprise retention posts which are flash molded onto the side of the connecting block during the molding operation. Upon insertion and positioning of a plurality of beam contacts within the connecting block housing, pressure is exerted against the retention posts thereby breaking the flash molding and forcing the posts through positioning holes in the contacts. Thereafter, the post tips are peened in place providing permanent but free floating connection between the contacts and the connecting block housing.
The use of the one-piece housing thereby overcomes the several deficiencies and disadvantages relative to the two-piece connecting block structures associated with the prior art; and thus decreases assembly time, inventory and tooling costs leading to an overall lower cost for the connecting block portion of the electrical wiring system.
The connecting block of U.S. Pat. No. 4,964,812 also overcomes the problem of inadequate end wall strength discussed above by making use of the free floating contact retention inherent to both the present invention and prior art designs. This improvement is accomplished by employing irregular contact spacing on the end positions of the connecting block module. As a result, the tendency for outside wall breakage is substantially reduced. Reduction in center spacing for the two end contact problems (typically by about "0.005 per side) allows for an increase in outside wall thickness by approximately 30% while also acting to inwardly bias the upper halves of the outside contact when mated with the wiring block. The free floating nature of the terminal clips easily allows for the non-cumulative spacing deviation between the outer two positions of the connecting block and wiring block without compromising connection integrity or compatibility with accessories common to both the present invention and prior art designs.
While well-suited for its intended purpose, there are many applications which necessitate that the connecting block be connected directly to a circuit board (or the like) as opposed to the receptacles of the wiring block. While connecting blocks of the type disclosed by in Berglund patent 4,118,095 are known which include a tail extension for soldering onto a circuit board (referred to as AT&T 110D Modules), there is presently no circuit mountable connecting block of the type described in U.S. Pat. No. 4,964,812.